Severity
Non-Event
Was Hydrogen Released?
No
Was There Ignition?
No
Incident Date
Jul 15, 2009
Setting
Equipment
  • Hydrogen Production/Use Systems
  • Water Electrolysis System
Damage and Injuries
Probable Cause
When Incident Was Discovered
Lessons Learned

The possible outcomes from new maintenance scenarios can be predicted by using an accurate simulation. The proposed filter change-out maintenance was studied to identify conditions to which the catalyst might be exposed and a mock-up of the filter, it's mounting/housing, and catalyst was assembled. Conditions selected to represent the worst case that could be encountered during a maintenance operation were reproduced. For the conditions of temperature and pressure, this included simulating the state of the catalyst. Oxygen was removed from the catalyst with a dry nitrogen purge, and followed by a graduated hydrogen purge from 0.5 to 10 % concentration. Hydrogenation was completed by then subjecting the catalyst to a purge of 100 % concentration of hydrogen. De-ionized water was vacuum-degassed for 10 minutes to remove oxygen, then saturated with hydrogen (by bubbling) at pressure. The simulation of pre-change-out filter conditions was completed by adding the hydrogen-saturated water to the hydrogenated catalyst within the mock-up system. The simulation of conditions introduced by the proposed maintenance was accomplished by draining the water and introducing a purge of oxygen-enriched air (ISS ambient conditions). The drained water and purged air were captured for laboratory analysis to check for thermal degradation and toxic byproducts of Teflon. Gas Chromatography with Mass Spectral detection (GC-MS) revealed no fluorinated species above the detection limits in the gas phase, and Ion Chromatography (IC) identified only small amounts of fluorinated compounds in the liquid phase (not indicative of a handling hazard). Post-test thermal gravimetric analysis (TGA) of samples indicated that insufficient heat was generated in the tests to thermally decompose the Teflonized catalyst. The conclusion is that when charged catalyst is handled wet, reactions with air are reduced to the point of permitting safe handling. A caution is noted. While deliberate simulation of conditions that would result in rapid exposure to dry charged catalyst was not performed, the hydrogenation step, if not initially done gradually, but with 100 % concentration hydrogen, will produce smoke and steam, suggesting any procedure that introduces rapid exposure to air could result in high temperatures and potentially hazardous by-products.

Maintenance on PEM technology systems that involves accumulated catalyst within filters may be safely performed by reducing the rate of exposure of catalyst materials to air or oxygen, always keeping a coating of water on catalyst surfaces and making sure discarded catalyst is properly disposed and not allowed to dry out, especially in the presence of volatile and flammable materials. Catalyst materials exposed for a time in a hydrogen environment will absorb substantial amounts of hydrogen, becoming "activated". Subsequent exposure to air or oxygen without mitigating steps can cause high temperatures to occur on catalyst surfaces, creating a potential fire hazard. Do not expose Teflon to high temperatures.

Key:

  • = No Ignition
  • = Explosion
  • = Fire
Hydrogen Incident Summaries by Equipment and Primary Cause/Issue
Equipment / Cause Equipment Design or Selection Component Failure Operational Error Installation or Maintenance Inadequate Gas or Flame Detection Emergency Shutdown Response Other or Unknown
Hydrogen Gas Metal Cylinder or Regulator   3/31/2012
4/30/1995
2/6/2013
4/26/2010 12/31/1969     3/17/1999
11/1/2001
12/23/2003
Piping/Valves 4/4/2002
2/2/2008
5/11/1999
4/20/1987
11/4/1997
12/31/1969
8/19/1986
7/27/1991
12/19/2004
2/6/2008
10/3/2008
4/5/2006
5/1/2007
9/19/2007
10/31/1980
2/7/2009 1/24/1999
2/24/2006
6/8/1998
12/31/1969
2/7/2009

9/1/1992
10/31/1980

10/3/2008  
Tubing/Fittings/Hose   9/23/1999
8/2/2004
8/6/2008
9/19/2007
1/1/1982 9/30/2004
10/7/2005
  10/7/2005  
Compressor   10/5/2009
6/10/2007
8/21/2008
1/15/2019
    10/5/2009 8/21/2008  
Liquid Hydrogen Tank or Delivery Truck 4/27/1989 12/19/2004
1/19/2009
8/6/2004 12/31/1969   1/1/1974 12/17/2004
Pressure Relief Device 7/25/2013
5/4/2012
1/15/2002
1/08/2007
12/31/1969        
Instrument 1/15/2019 3/17/1999
12/31/1969
2/6/2013
    11/13/73    
Hydrogen Generation Equipment 7/27/1999     10/23/2001      
Vehicle or Lift Truck   7/21/2011         2/8/2011
12/9/2010
Fuel Dispenser   8/2/2004
5/1/2007
6/11/2007
9/19/2007
  2/24/2006
1/22/2009
     
Fuel Cell Stack            

5/3/2004
12/9/2010
2/8/2011

Hydrogen Cooled Generator       12/31/1969
2/7/2009
     
Other (floor drain, lab
anaerobic chamber,
heated glassware,
test chamber,
gaseous hydrogen
composite cylinder,
delivery truck)
  11/14/1994
7/21/2011
7/27/1999
6/28/2010
8/21/2008
12/31/1969
3/22/2018
    6/10/2019
  • = No Ignition
  • = Explosion
  • = Fire